What are paving jointing mortars?
Paving jointing mortars (also called paving sand, jointing compound or resinbonded jointing material) are specially formulated mixtures that fill the spaces between individual paving units such as bricks, stones, concrete slabs or tiles. Their primary role is to lock the units together, control movement, prevent weed growth and provide a uniform, durable surface.
Unlike ordinary masonry mortar, jointing mortars are designed to be flexible enough to accommodate thermal expansion, traffic loads, and minor settlement while still maintaining enough strength to resist cracking and erosion.
Common Types of Jointing Mortars
1. Cementsand grout
A traditional mix of Portland cement, sharp sand and water. It is inexpensive and works well for dense, lowtraffic installations. However, it can be prone to shrinkage and is less tolerant of movement.
2. Polymeric sand
Fine sand blended with polymeric binders that harden when activated by moisture. It creates a hard, waterresistant joint while still allowing some flexibility. Ideal for residential driveways and patios.
3. Resinbonded jointing material
A mixture of fine aggregate and a twopart epoxy or acrylic resin. It offers excellent colour stability, high compressive strength, and superior resistance to weed growth. Used for hightraffic commercial areas and decorative installations.
4. Flexible jointing compounds
Based on latex or polyurethane binders, these compounds remain slightly elastic after curing, making them suitable for areas with frequent temperature changes or vehicular loading.
5. Premixed jointing mortars
Readytouse products sold in sealed bags. They contain a balanced blend of cement, sand, polymers and additives. They save time and reduce the risk of incorrect mix ratios.
| Type | Typical Use | Flexibility | Water Resistance | Cost (per m) |
|---|---|---|---|---|
| Cementsand grout | Garden paths, lowtraffic patios | Low | Moderate | Low |
| Polymeric sand | Residential driveways, pool decks | Medium | High | Medium |
| Resinbonded mortar | Commercial plazas, decorative paving | MediumHigh | Very high | High |
| Flexible compounds | Areas with temperature swing, roadways | High | High | MediumHigh |
| Premixed mortars | Quickinstall projects | Varies | Varies | Medium |
How to Choose the Right Jointing Mortar
- Traffic level: Heavy vehicular traffic calls for higher compressive strength and better wear resistance (e.g., resinbonded or flexible compounds).
- Climate: In freezethaw zones, select a mortar with low water absorption and some flexibility to accommodate expansion.
- Colour match: Many polymeric sands are tinted to match common paving colours; this helps achieve a seamless appearance.
- Installation speed: Premixed or polymeric sands cure quickly and are ideal for projects with tight timelines.
- Maintenance expectations: For areas where weed growth is a concern, a polymeric or resinbonded product offers superior weed resistance.
StepbyStep Application Guide
- Prepare the substrate: Sweep away debris, dust, and loose material. The surface must be clean and slightly damp (not wet).
- Lay the paving units: Position bricks, stones or slabs to the desired pattern. Ensure uniform joint width (usually 36mm for residential work).
- Choose the mortar: Based on the criteria above, select the appropriate product.
- Mix (if required): For cementsand grouts, combine cement, sand and water to a peanutbutter consistency. Follow manufacturers watertocement ratio.
- Apply the mortar:
- For sandbased products, spread the material over the surface and sweep it into the joints with a broom.
- For liquid or resinbased compounds, pour onto the joints and use a jointfinisher or trowel to push the material fully into the gaps.
- Compact and clean: Firmly vibrate or tap the paving to settle the jointing material, then remove excess from the surface with a soft brush or vacuum.
- Curing: Keep the joints moist (if required) for the period recommended by the manufacturer typically 2448hours for cementbased systems and 46hours for polymeric sand.
- Final inspection: Check that all joints are completely filled, the surface is level, and there are no loose spots.
Safety tip: Wear gloves and eye protection when handling polymeric or resinbased mortars, as the chemicals can cause skin irritation.
Maintenance and Longevity
Properly installed jointing mortar can last many years, but routine care extends its service life:
- Regular cleaning: Sweep away leaves and grit to prevent moisture entrapment that leads to freezethaw damage.
- Rejointing: In hightraffic zones, joints may wear down. Reapply the chosen mortar after cleaning the gaps.
- Weed control: Even weedresistant products can develop growth if organic matter accumulates. Use a nonchemical weed puller or a light powerwash.
- Sealants: Some resinbonded mortars benefit from an additional clear sealant to enhance UV stability.
Inspect the paving at least once a year for cracking, erosion or settled joints. Early repair prevents larger structural issues.
